1. Field of Invention
The present invention relates to progressive die assemblies that are used to manufacture relatively large diameter annular components, such as stator cores for electric motors.
2. Description of Related Art
It is well known to manufacture annular laminated parts, such as stator cores, in a manner in which individual annular laminations are stamped from a strip of steel stock material by a progressive die apparatus and are stacked and interlocked to form the part.
However, because each annular lamination is formed as a single piece, the width of the steel strip needs to be at least as large as the outer diameter of the lamination. Thus, disadvantageously, a relatively large amount of the steel material is wasted when manufacturing annular laminated parts via known processes, for example, the material between adjacent laminations and within the interior of each lamination.
In the past, material waste was minimized by manufacturing a rotor core from the central portion of the stator laminations and/or by stamping the stator laminations in rows that were staggered with respect to one another. However, with the use of relatively new electrically commutated motors (ECM), which do not include a rotor core, material waste is much more of a concern as, for example, a central portion of large diameter stator lamination which is stamped as an annular part may remain unused.
A need exists for a high speed die assembly or assemblies capable of creating relatively large diameter annular laminated parts without excessive waste of the stock material from which the annular laminated parts are formed.